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The effect of hempseed in the diet of laying hens was evaluated at 0, 30, 60 and 90 g/kg concentrations. The aim of the study was to determine the effect of dietary treatment on the performance of hens, the physical characteristics of egg quality, the concentrations of α- and γ-tocopherol and the carotenoid and cholesterol contents of egg yolks, together with the breaking strength of tibial measurements. In light of the obtained results, our study aimed to address the optimal dietary level of hempseed in laying hen diets. Lohmann Brown hens (n = 240) were divided into 4 dietary treatment groups (6 cages per treatment) with 10 hens per cage. The experiment lasted for 12 weeks. The level of nutrients in all diets (wheat-corn) was well balanced. The dietary metabolisable energy was adjusted using rapeseed oil. The addition of 30 g/kg of hempseed to the diet significantly increased (P˂0.001) egg production and egg mass. Alpha-tocopherol increased significantly (P = 0.002) only in the case of the 60 g/kg hempseed level (101 mg/kg dry matter (DM) versus 83 mg/ kg DM in the control group). In contrast, the level of γ-tocopherol increased gradually from 11 mg/kg DM in the control to 29, 39 and 43 mg/kg DM at the 30, 60 and 90 g/kg levels of dietary hempseed, respectively. The concentrations of beta carotene, zeaxanthin and lutein in egg yolks were not influenced by the dietary treatment. Hempseed at 90 g/kg (P = 0.036) decreased egg shell thickness without affecting its strength. The addition of hempseed decreased (P˂0.001) the cholesterol concentration in the egg yolks in all experimental groups. The addition of 30, 60 and 90 g hempseed increased (P˂0.001) the breaking strength of the tibia to 354, 352 and 350 N, respectively, compared to 297 N in the control group. The highest level of hempseed in the diet positively influenced the Ca concentration in the tibia (P = 0.021). The concentration of P in the tibia was negatively affected in the 60 to 90 g/kg hempseed treatments (P˂0.001). Eggs are a significant source of α-tocopherol. Based on our results, there is a possibility for enrichment of egg yolks with γ-tocopherol, with all of its associated health benefits, by the addition of hempseed to the diet of laying hens. Another significant benefit of hempseed is its effect on the breaking strength of the tibia, which can help with crucial problems in the commercial breeding of laying hens.

Tocopherol is an important lipid-soluble antioxidant beneficial for both human health and plant growth. Here, we fine mapped a major QTL- qVE1 affecting γ -tocopherol content in maize kernel, positionally cloned and confirmed the underlying gene ZmPORB1 ( por1 ), as a protochlorophyllide oxidoreductase. A 13.7 kb insertion reduced the tocopherol and chlorophyll content, and the photosynthetic activity by repressing ZmPORB1 expression in embryos of NIL-K22, but did not affect the levels of the tocopherol precursors HGA (homogentisic acid) and PMP (phytyl monophosphate). Furthermore, ZmPORB1 is inducible by low oxygen and light, thereby involved in the hypoxia response in developing embryos. Concurrent with natural hypoxia in embryos, the redox state has been changed with NO increasing and H 2 O 2 decreasing, which lowered γ -tocopherol content via scavenging reactive nitrogen species. In conclusion, we proposed that the lower light-harvesting chlorophyll content weakened embryo photosynthesis, leading to fewer oxygen supplies and consequently diverse hypoxic responses including an elevated γ -tocopherol consumption. Our findings shed light on the mechanism for fine-tuning endogenous oxygen concentration in the maize embryo through a novel feedback pathway involving the light and low oxygen regulation of ZmPORB1 expression and chlorophyll content.

Tocopherols are lipophilic antioxidants that are synthesized exclusively in photosynthetic organisms. In most higher plants, α- and γ-tocopherol are predominant with their ratio being under spatial and temporal control. While α-tocopherol accumulates predominantly in photosynthetic tissue, seeds are rich in γ- tocopherol. To date, little is known about the specific roles of α- and γ-tocopherol in different plant tissues. To study the impact of tocopherol composition and content on stress tolerance, transgenic tobacco (Nicotiana tabacum) plants constitutively silenced for homogentisate phytyltransferase (HPT) and γ-tocopherol methyl transf erase (γ-TMT) activity were created. Silencing of HPT lead to an up to 98% reduction of total tocopherol accumulation compared to wild type. Knockdown of γ-TMT resulted in an up to 95% reduction of α-tocopherol in leaves of the transgenics, which was almost quantitatively compensated for by an increase in γ-tocopherol. The response of HPT and γ-TMT transgenics to salt and sorbitol stress and methyl viologen treatments in comparison to wild type was studied. Each stress condition imposes oxidative stress along with additional challenges like perturbing ion homeostasis, desiccation, or disturbing photochemistry, respectively. Decreased total tocopherol content increased the sensitivity of HPT:RNAi transgenics toward all tested stress conditions, whereas γ-TMT-silenced plants showed an improved performance when challenged with sorbitol or methyl viologen. However, salt tolerance of γ-TMT transgenics was strongly decreased. Membrane damage in γ-TMT transgenic plants was reduced after sorbitol and methyl viologen-mediated stress, as evident by less lipid peroxidation and /or electrolyte leakage. Therefore, our results suggest specific roles for α- and γ-tocopherol in vivo.

The main research activities of the last decades on tocopherols were mainly focused on alpha-tocopherol, in particular when considering the biological activities. However, recent studies have increased the knowledge on gamma-tocopherol, which is the major form of vitamin E in the diet in the USA, but not in Europe. gamma-Tocopherol provides different antioxidant activities in food and in-vitro studies and showed higher activity in trapping lipophilic electrophiles and reactive nitrogen and oxygen species. The lower plasma levels of gamma- compared to alpha-tocopherol might be discussed in the light of different bioavailability, but also in a potential transformation from gamma- into alpha-tocopherol. From the metabolism end product, only that of gamma-tocopherol (2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxychroman), but not that of alpha-tocopherol, was identified to provide natriuretic activity. Studies also indicate that only the gamma-tocopherol plasma level served as biomarker for cancer and cardiovascular risk. Therefore, this paper provides a comprehensive review on gamma-tocopherol with emphasis on its chemistry, biosynthesis, occurrence in food, different intake linking to different plasma levels in USA and Europe, absorption and metabolism, biological activities, and possible role in human health.

The intestinal absorption of cholesterol and lipid micronutrients such as vitamin E has been shown to share some common pathways. The present study aims to further compare the uptake of cholesterol ([H-3] cholesterol v. 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3-ol (NBD-cholesterol)) and tocopherol in Caco-2 TC-7 cells and in mouse intestine, with special focus on the respective roles of scavenger receptor class B type I (SR-BI) and Niemann-Pick C1-like 1 (NPC1L1). Conversely to NBD-cholesterol, the uptakes of [H-3] cholesterol and tocopherol by Caco-2 cells were impaired by both block lipid transport-1 and ezetimibe, which inhibit SR-BI and NPC1L1, respectively. These inhibitions occurred only when cholesterol or tocopherol was delivered to cells included in micelles that contained biliary acid and at least oleic acid as a lipid. In vivo, after 2 h of digestion in mice, the uptake of the two cholesterol analogues and of tocopherol all showed distinct patterns along the duodenum-jejunum axis. [H-3] Cholesterol uptake, which correlated closely to NPC1L1 mRNA expression in wild-type (wt) mice, was strongly inhibited by ezetimibe. Intestinal SR-BI overexpression did not change NPC1L1 expression and led to a significant increase in [H-3] cholesterol uptake in the distal jejunum. Conversely, neither ezetimibe treatment nor SR-BI overexpression had an effect on NBD-cholesterol uptake. However, in contrast with SR-BI mRNA expression, tocopherol absorption increased strongly up to the distal jejunum in wt mice where it was specifically inhibited by ezetimibe, and was increased in the proximal intestine of intestinal SR-BI-overexpressing mice. Thus, cholesterol and tocopherol uptakes share common pathways in cell culture models, but display different in vivo absorption patterns associated with distinct contributions of SR-BI and NPC1L1.

Tocopherols, synthesized by photosynthetic organisms, are micronutrients with antioxidant properties that play important roles in animal and human nutrition. Because of these health benefits, there is considerable interest in identifying the genes involved in tocopherol biosynthesis to allow transgenic alteration of both tocopherol levels and composition in agricultural crops. Tocopherols are generated from the condensation of phytyldiphosphate and homogentisic acid (HGA), followed by cyclization and methylation reactions. Homogentisate phytyltransferase (HPT) performs the first committed step in this pathway, the phytylation of HGA. In this study, bioinformatics techniques were used to identify candidate genes, slr1736 and HPT1, that encode HPT from Synechocystis sp. PCC 6803 and Arabidopsis, respectively. These two genes encode putative membrane-bound proteins, and contain amino acid residues highly conserved with other prenyltransferases of the aromatic type. A Synechocystis sp. PCC 6803 slr1736 null mutant obtained by insertional inactivation did not accumulate tocopherols, and was rescued by the Arabidopsis HPT1 ortholog. The membrane fraction of wild-type Synechocystis sp. PCC 6803 was capable of catalyzing the phytylation of HGA, whereas the membrane fraction from the slr1736 null mutant was not. The microsomal membrane fraction of baculovirus-infected insect cells expressing the Synechocystis sp. PCC 6803 slr1736 were also able to perform the phytylation reaction, verifying HPT activity of the protein encoded by this gene. In addition, evidence that antisense expression of HPT1 in Arabidopsis resulted in reduced seed tocopherol levels, whereas seed-specific sense expression resulted in increased seed tocopherol levels, is presented.

Alpha and gamma tocopherol metabolism in healthy subjects and patients with end-stage renal disease. The metabolism of alpha and gamma tocopherol, the major components of vitamin E, have not been studied in uremic patients. The major pathway of tocopherol metabolism is via phytyl side chain oxidation, leaving carboxyethyl-hydroxychromans (CEHC) as metabolites. Alpha and gamma CEHC are water soluble, renally excreted, with known potent anti-inflammatory and antioxidative properties. We examined serum alpha and gamma tocopherol and respective CEHC concentrations in 15 healthy subjects and 15 chronic hemodialysis patients. Serum alpha tocopherol levels were similar in hemodialysis patients (12.03 ± 1.34 μg/mL) and healthy subjects (11.21 ± 0.20 μg/mL), while serum gamma tocopherol levels were significantly greater in hemodialysis patients (3.17 ± 0.37 μg/mL) compared to healthy subjects (1.08 ± 0.06 μg/mL, P < 0.0001). Serum alpha and gamma CEHC levels were tenfold and sixfold higher in hemodialysis patients compared to healthy subjects, respectively (both P < 0.0001). Serum alpha and gamma tocopherol levels and CEHC metabolites were also measured after supplementation of alpha- or gamma-enriched mixed tocopherols in both hemodialysis patients and healthy subjects. Tocopherol administration resulted in modest or nonsignificant changes in serum tocopherol concentrations, while markedly increasing serum CEHC concentrations in both healthy subjects and hemodialysis patients. Hemodialysis resulted in no change in the serum alpha or gamma tocopherol concentrations while decreasing serum alpha CEHC and gamma CEHC levels by 63% and 53%, respectively (both P = 0.001 versus predialysis). Fourteen-day administration of gamma-enriched but not alpha tocopherols lowered median C-reactive protein (CRP) significantly in hemodialysis patients (4.4 to 2.1mg/L, P < 0.02). First, serum alpha and gamma CEHC accumulate in uremic patients compared to healthy subjects; second, supplementation with tocopherols dramatically increases serum CEHC levels in both healthy subjects and hemodialysis patients; and, finally, CEHC accumulation may mediate anti-inflammatory and antioxidative effects of tocopherols in hemodialysis patients.

We generated transgenic rice plants overexpressing Arabidopsis thaliana ρ-hydroxyphenylpyruvate dioxygenase (HPPD), which catalyzes the first committed step in vitamin E biosynthesis. Transgenic grains accumulated marginally higher levels of total tocochromanols than controls, reflecting a small increase in absolute tocotrienol synthesis (but no change in the relative abundance of the α and γ isoforms). In contrast, there was no change in the absolute tocopherol level, but a significant shift from the γ to the α isoform. These data confirm HPPD is not rate limiting, and that increasing flux through the early pathway reveals downstream bottlenecks that act as metabolic tipping points.

Gamma tocopherol (gT) exhibits beneficial cardiovascular effects partly due to its anti-inflammatory activity. Important sources of gT are vegetable oils. However, little is known to what extent gT can be transferred into marine animal species such as Atlantic salmon by feeding. Therefore, in this study we have investigated the transfer of dietary gT into salmon. To this end, fish were fed a diet supplemented with 170 ppm gT for 16 weeks whereby alpha tocopherol levels were adjusted to 190 ppm in this and the control diet. Feeding gT-rich diets resulted in a three-fold increase in gT concentrations in the liver and fillet compared to non-gT-supplemented controls. Tissue alpha tocopherol levels were not decreased indicating no antagonistic interaction between gamma- and alpha tocopherol in salmon. The concentration of total omega 3 fatty acids slightly increased in response to dietary gT. Furthermore, dietary gT significantly decreased malondialdehyde in the fillet, determined as a biomarker of lipid peroxidation. In the liver of gT fed salmon we observed an overall down-regulation of genes involved in lipid homeostasis. Additionally, gT improved the antioxidant capacity by up-regulating Gpx4a gene expression in the pyloric caeca. We suggest that Atlantic salmon may provide a marine functional source capable of enriching gT for human consumption.

The quantity and composition of tocopherols (compounds with vitamin E activity) vary widely among different plant species reflecting the expression, activity and substrate specificity of enzymes in the corresponding metabolic pathway. Two Arabidopsis cDNA clones corresponding to q-hydroxyphenylpyruvate dioxygenase (HPPD) and 2-methyl-6-phytylplastoquinol methyltransferase (MPBQ MT) were constitutively expressed in corn to further characterize the pathway and increase the kernel tocopherol content. Transgenic kernels contained up to 3 times as much c-tocopherol as their wild type counterparts whereas other tocopherol isomers remained undetectable. Biofortification by metabolic engineering offers a sustainable alternative to vitamin E supplementation for the improvement of human health.